System of indicating distance



Nov. 9, 1937. E. w. GENT SYSTEM OF INDICATING DISTANCE Filed Dec. 21, 1935 w a; Q v A w E 2 a m 3 a 2 a 2 9 w \l 6 GR w 2 l 7 mm 3 RM 5 w a C Q 2 A?! a a Q I H Fu u ml n V {MM '7. I V a E a q 4 E9 3 GR 5 Wm M M4 Mm; E. W. GENT VJ A T TORNEV Patented Nov. 9, 3937 warren states I attain SYSTEM OF INDECATING DISTANCE Edgar W. Gent, Morristown,

Laboratories, incorporated, a corporation of New York Bell Telephone New York, N. Y.,

N. J assignor to 1 Application December 21,1935, Serial No. 55,589

5 Claims.

This invention relates to a system of indicating distance and more particularly to a. system for measuring the altitude of an airplane above the terrain.

An object of this invention is to ascertain distance;

A more particular object of this invention is to obtain on an aircraft a quick and accurate determination of the altitude of the aircraft.

Systems have heretofore been proposed for ascertaining the altitude of an airplane above the terrain. Some of these systems require frequent adjustment of the apparatus resulting in constant attention of the airplane pilot, while with other systems the indication of the altitude is difiicult to discern. These systems are particularly disadvantageous when an airplane approaches an airport to land. The plane within a few seconds frequently descends from several hundred feet to a few feet'above the airport runway. During'this period the pilot is especially occupied and a clear, quick and accurate indication of the altitude of the airplane without any adjustment of apparatus is highly desirable for the proper landing of the plane.

In accordance with this invention, an indication of the altitude of an aircraft is obtained by observation fa plurality of illuminating devices. Each of these devices indicates a particular range of distances. When the altitude of the airplane above ground is within one of these ranges, the device corresponding to that particular range becomes illuminated. The altitude of the plane within the range is ascertained by observing the portion of the device which is exposed to View. a

In a specific embodiment, a sound wave is transmitted at predetermined intervals. After reflection on the ground, the wave actuates thedischarge of one of a. plurality of neon tubes corresponding to the range of altitude within which the airplane is located at the time. A

shutter'having opaque and transparent portions constantly rotates in front of eachwof the tubes or in front of a slitilluminated by the tubes.

The shutter is adjusted so that when at the distance of one limit of the particular range of distances corresponding to the tube, the opaque portion of the shutter completely covers the tube or slit, while at the other limit the'tube or slit is completely exposed by the transparent portion of the shutter. The-rotationis such that the v opaque portion is gradually removed from one limit to the other and the portion of .opaque coveringof the tube or slit is dependent upon conducting portion of-the contact the transmitter 8,

the distance or the. altitude within the particularrange of the tube. According y, when the sound wave actuates the discharge of a neon tube corresponding to a particular range, the height of the airplane is indicated by observing the propor-= tion of, illumination of the tube or slit which is visible. A suitably calibrated scale is associated witheach tube to aid in this observation.

A more comprehensive understanding of this invention is obtained by reference to .the accompanying drawing, in which:

Fig. 1 is a schematicadiagram of an embodiment of this invention; and

Fig. 2 is a schematic diagram of'ano'ther embodiment of this invention.

1 Fig. 1 shows a sonic altimeter in accordance with this invention employed on an airplane i. Aconstantly rotating motor 2 rotates a shaft 3.- Fixedly attached to'the shaft 3 are a contact wheel 4 anda conducting wheel 5. The conducting wheel 5 is continuously in contact with a brush 8 connected to one Read 9 of a transmitter 8. The transmitter 8 is preferably of the directional type and is located on the under side of the airplane i. Another lead ill of the transmitter 8 is connected to one terminal of an in-' 25 ductor-alternator H. The inductor-alternator H is of the type described in an article entitled Inductor Alternators for Signalling Purposes by F. W. Merrill, published in Electrical Engineering, January 1934, vol. 53, No. 1, pages 78 to 94. The inductor-alternator is preferably capable of generating a frequency of from two thousandto' nine thousand cycles per second. The other terminal, of the inductor-alternator is connected to a contact? in engageable relation with the peri'phery of the contact wheel 5. The periphery of the contact wheel 5 is constructed of insulated and conducting portions so that fora brief interval during each revolution of theshaft 3 the I wheel 4 engages the contact-l to provide a series connection through the shaft 3, conducting wheel 5 and contact 6 between the inductor-alternator l1 vand When the inductor-alternator .l1is connected to the transmitter 8 by the engagement of the conducting portion of the co ct wheel 4 .with the contact I, a wave or' train 0 waves is-transmitted by the transmitter 8; When these waves pass through the air to they are reflected therefrom. The reflected aves are impressed upon a microphone U do ected to a receiving amplifier indicated by a block diagram in the drawing. The receiv- 3 of the waves transmitted by the transmitter 8. The reflected waves, after amplification by the receiving amplifier pass through a pair of leads l2 to the terminals of a toroidal illuminating device l3. While the device [3 may be any type of illuminating device, it is preferably of the type which is filled with neon gas and known commercially as a neon lamp or tube. A circular shutter l4 fixedly attached to the shaft 3 and having a slit l5 therein serves to completely cover the tube l3 from view with the exception of the small portion observed through the slit 5. A

alternator l1 to the transmitter 8, a wave or train of waves is transmitted by the transmitter 8. The wave or train of waves, after passage through the air or other molecular medium and reflection upon the terrain, is impressed upon the microphone II. The received wave or train of waves is amplified by the receiving amplifier and the current in the output of the amplifier illuminates the neon device or tube l3. A portion of the illuminated tube is exposed to view by the slit l5 in the circular shutter l4. Since the position of the slit l5 depends upon the rotation of the shutter l4 or the time elapsing between the transmission of the waves and their reception by the microphone to illuminate the tube I3, the position of the slit indicates the distance of the airplane above the terrain. The circular scale 16 aids in this determination. The slit l5 can be so located on the-circular shutter I4 that it is immediately adjacent to the zero reading on the scale when the contact I engages the conducting portion of thecontact wheel 4 to transmit a wave or train of waves. The circular distance traversed by the slit around the scale is correlated directly with the distance of the airplane above the terrain. The speed of the motor 2 is adjusted so that the shaft 3 revolves one completerevolution during the time required for a wave to travel from the airplane to the terrain and return to the plane after reflection for the maximum altitude to be-ascertained.

Fig. 2 shows a-distance which a plurality of illuminating devices are emplayed, each device capable of indicating a different range of distances. A shaft M is rotated at a uniform speed by a motor 20. A contact wheel 22 with an elevation on its periphery controls a pair of contacts 23 in engageable relation with the periphery of the contact wheel 22. Dur- 11 transmitter 8,

ing a brief interval of the rotation of the contact wheel 22, the elevation on the periphery thereof results in the engagement of the contacts 23. At all other times of a complete revolution of the wheel 22, the contacts 23 are disengaged. One of the contapts 23 is connected to lead 9 of connected to one terminal of an inductor-alternator I1. The other terminal of the inductoralternator I1 is connected by means of a lead 16 to the transmitter 3 and the inductor-alternator l1 shown in Fig. 2 are identical with the same apparatus in Fig. 1. During the normal operation of the system shown 'stantly engageable with the ring-50.

connect the inductor-' determining system in.

while the other contact 23 is 8. Both the transmitter aware? in Fig. 2, the motor associated with the inductoralternator is continuously rotating. When the contacts 23 engage during a brief interval of each rotation of the shaft 2|, the inductor-alternator I1 is connected to the transmitter 8 to transmit I a wave or train, of waves.

Three sectional slip rings 25, 26 and 21 are fixedly attached to the rotatable shaft 2!. Each of the rings 25,26 and 21 has an insulated and a conducting portion on its periphery. The conducting portion of each of the rings 25, 26 and 21 is connected electrically to one'lead of a receiving amplifier indicated by the block diagram in the drawing. The connection to this lead of the receiving amplifier is accomplished through a collector ring 50 fixedly attached to the shaft 2| and a brush 5| connected to the lead and con- Contacts 35, 36, and 31 are in engageable relation with the peripheries of the rings 25, 26, and 21, respectively. Three neon illuminating devices 28, 29 and 30 are connected, respectively, to the contacts 35, 36 and 31. The other terminals of the devices 28, 29 and 36 are connected to the other lead of the receiving amplifier. The engagement of'the conducting portion of the peripheries of the rings 25, 26 and 21 with their respective contacts 35, 36 and 31 results in a connection through the rotatable shaft 2| from the receiving amplifier to the terminal of the lamp with which the particular engaged contact and contact wheel are associated. A microphone 3| is connected to the input of the receiving amplifier. Both the microphone 3i and the transmitter 8 are located on the under side of an airplane 32.

When a wave or train of waves after reflection on a surface is impressed upon the microphone 3!, one of the devices 28, 29 or 30 is illuminated depending upon which of the contacts 35, 36 or 31 engages the conducting portion of its respectively associated contact wheel. The conducting portions of the rings 25, 26 and 21 are such and the rings 25, 26 and 21 are fixedly attached to the shaft 2| so that the device 28 becomes illuminated if the airplane 32 is within the lowest range desired to-be estimated. Device 30 is illuminated if the airplane is within the highest range desired to be ascertained and device 29 if the plane is with a range intermediate between the lowest and highest range. If, for example, device 28 is illuminated when the airplane is 1 to 50 feet above the terrain, lamp 29 when the plane. is 50 to 150 feet above the terrain and tube 36 when the plane is 150 to 550 feet above the surface, the conducting portion of the ring 25 is one-twelfth of the circumference of the ring 25, ring 26 two-twelfths, and ring 21 eight-twelfths. This proportion of the circumference includes a small overlap of the distances between the various ranges, The ring 25 is fixedly attached to the shaft 2| so that the contact 35 engages with the conducting portion of the ring 25 a short interval after the contact 23 becomes engaged. This interval corresponds to the period required for a wave to travel 2 feet or slightly more than the distance between the transmitter 24 and. the microphone 3| if no baflle between the 'microphone and transmitter is employed. Accordingly, the device 28 is not illuminated as a result of the direct transmission of waves from the transmitter' to the microphone. The ring 26 is fixedly attached to the shaft 2| so that the contact 36 engages the conducting portion of the ring 26 immediately prior to the time at which the contact 35 disengages from the ring'25. Likewise,

' .ing to the range of the tube as, .the tube 28 is the range indicated by the tube 8% 'A scale 46 intervals, a wave-or train ofwaves is transmit- 70 g produce currents in the output of the receiving amplifier lac-illuminate one of the plurality of tion or said signal back to the airplane and coopwith the tube 2s and is rotated by the drive access? g the contact 37 engages with the conducting pc tion of the. ring 21 immediately prior to the diengagement of the contact 36 withthe conducting portion of the periphery of the ring 2d. The speed of the motor 28 is adjustedso that the shaft 2i revolves one complete revolution in a period of time-corresponding to the highest limit of the maximum range of altitude to be esti mated.

Fixedly attached to the shaft 23 is a gear 33] A plurality of gears 3d are in engageable relation with the gear at to rotate a drive sprocket 55 at approximately ii revolutions per 'seccnd, a drive sprocket 56 at apprommately 5.6 revolutions per second, and a. drive sprocket 57: at approximately 9 revolution per second if the maximum distance to be indicated by devices 28 29 and '30 are approximately 50, 150 and 550 feet, respectively, and the molecular medium through which the waves pass is air. The rate of rotation of the sprockets 55, 56 and 5! depends upon the range of distances to be indicated. The time required for rotation of each of the sprockets is that for a wave to travel from the system to a reflecting surface and return to the system in the maximum distance to be indicated by the illuminating devices with which each of the sprockets is respec- What is claimed is: tively associated. The drive sprockets 55, 56 and 1. A sonic altimeter for airplanes comprising 57 are capable of rotating 16 millimeter motion means for transmitting alongitudinal wave at picture film. A circular band film 39 having predetermined intervals, a plurality oi'igaseous opaque and transparent portions is driven by the drivesprocket 55 and rotated with-the aid of another sprocket 38 in front of the tube 28. The opaque and transparent portions of the band of film are situated so that the opaque portion completely covers the tube at the beginning of the range. During the interval of time correspondairplane is located, The distance within any one of the particular ranges is indicated by the ated rotating band shutter and scale. The three devices or tubes 28, as and 3@ may be nested close together behind a plate bearing the calibrated .values of the range of distances corresponding to each tube and the whole unit ed upon the instrument panel of an airplane. To further aid in identifying the particular range of distances, each tube may be different in color. For example, tube 28 may be. red, tube 29 blue and tube 30 green. Instead of the inductor-alternator may be employed. 7

Although the distance determining systems are described for use in airplanes, these systems are equally applicable to ships for depth determination at sea.

scribed, various modifications therein may be made without departing from the scope of the appended claims.

ranges oi distances to be-indicated, means responsive to said wares after passing through a of said devices to indicate the particular range "of distances traveled by said-longitudinal wave, and means associated with each of said devices for indicating the distance within said-range through which said longitudinal wave has traveled. 4

2. In an altimeter for an airplane, a plurality of gaseous, space discharge devices, a movable shutter located adjacent each of said devices, each shutter having an opaque section and a transparent section, control means for transmitting a signal from said airplane to earth, for partially completing circuits to light said devices consecugradually exposed to view to an observer located in front of the film by the gradual movement of the transparent portion of the film in front of the tube 28. At the end of the time interval corresponding to the highest limit of the range of distances which the tube 28 indicates, the entire length of the tube 28 is observed through the transparent portion of the film. In this mannor, the approximate location of the airplane within therange indicated by the tube 28 is ob= served. A scale at located immediately adjacent to the band film 39 aids in this determination. In a like manner, a band .film it is associated respect to the associated devices, said shutters being positioned with respect to the associated devices to bring transparent sections of the different shutters consecutively in position adjacent the associated devices at times when the circuits of the devices may be completed, andmeans operative upon reflection or the signal back to the airplane and'cooperating with said control means for lightingone of said devices to indicate the distance to earth below the airplane.

3. In a system for determining the distance of an airplane irom ground, a plurality of gaseous space discharge devices, a scale positioned ad-- sprocket 56 with the aid of another sprocket 62. The transparent portion of the film indicates the distance that the airplane 82 is located within the range indica'fted by thetube 29. A scale 58 located immediately adjacent to the film M assists in this determination of the distance within the range. A transparent and opaque band film d5 rotated by the drive sprocket 57 around another sprocket dd indicates the distance within similar to the' scale '40 located immediately adshutters each having a transparentsectiofi and jacent to the film d5 shows the distance within an opaque section, said shutters being respectively the range. The scales l0, l3 and 8B are preferpositioned adjacent said devices, control means ably calibrated empirically to'indicate the disfor transmitting a signal from the airplane totance within their respective ranges. H

when the contacts 23 engage at predetermined at diflerent speeds to bring the. transparent secposition adjacent thefa'ssociated devices and for partially completing Ph'cuits through the devices when the transparent section of a shutter is optedby theitransmittier 8. After reflection on the terrain, the reflected waves are impressed .upon the microphone 3!. The impressed waves neon tubes 28, 29 or 3l, -depending upon the grating with said control means fol-igniting ne proportion of the illuminated neon tubes exposed to view to an observer by its respectively associ-' of three tubes, plates and shutters maybe mountground, for efiecting movement 01 said shutters posite a devicey-and means eflective upon reflec particular range of distances within which the I ii, any other source of sonic or supersonic waves While preferred embodiments of this invention have been illustrated and de- I 30 space discharge devices corresponding to diflerent molecular medium for selectively discharging one tively, and for moving each of said shutters with iace'nt each of said devices, a plurality of movable tions of the different shutters consecutively in v of saidv devices to indicate the distance of the airplane from ground according to the device which is ignited and according to the exposed portion of the ignited device with respect to the scale associated therewith. i

4. In an'altimeter for an airplane, a plurality of gaseous space discharge devices, a movable shutter located adjacent each of said devices, each shutter having an opaque section and a transparent. section, means for operating said shutters at different speeds to bring transparent sections of the shutters consecutively in position adjacent the associated devices, control means for transmitting a signal from the airplane to earth and for partially completing circuits through said devices at times when the transparent sections of the shutters are'in position adjacent the devices, and means operative upon reflection of the signal back to the airplane and cooperating with said control means for lighting one of said devices to indicate the distance to earth below the airplane according to the device which is ignited.

5. In an altimeter for an airplane, a plurality of gaseous space discharge devices for indicating different ranges of distances when ignited, means for transmitting a longitudinal wave signal at predetermined intervals from the airplane and for consecutively preparing circuits for igniting said devices, means responsive to the reflected signal for completing one of the circuits through one o! the devices according to the distance traveled by the signal to indicate the range of distances traveled by the signal, and means associated with each of said devices for indicating the distance within the range through which said longitudinal wave has traveled.

, EDGAR W. GENT. 

